REPORT ON THE TETRACTINELLIDA. 
79 
Genus 2. Pcecillastra^ n. n. 
Normania, Bowerbank, Brit. Assoc. Rep., p. 328, 1868. 
Theneidse not possessing specialised poriferous recesses ; usually of plate-like form, 
bearing incurrent pores on one face, and small evenly dispersed oscules on the other. The 
megascleres are not radiatcly arranged ; and, in addition to trisenes occupying the usual 
position, calthrops are present within the choanosome. The microscleres are microxeas and 
spirasters, the former forming a loose felt throughout the sponge. 
Poecillastra schulzii, Sollas (PI. IX.). 
Normania scliulzii, Solias, Prelim. Account, Sci. Proc. Roy. Dubl. Soc., vol. v. p. 185, 1886. 
Sponge (PI. IX. fig. 1). — A thick plate-like growth, with rounded margins, erect, 
fiahelliform or vase-shaped ; attached ; surface even ; rough to touch ; pores on the outer 
side in generally dispersed cribriform areas ; oscules small, evenly dispersed on the inner 
side ; excurrent canals, small and numerous, entering the wall more or less transversely, 
separated by intervals usually less than their own diameter from each other near 
their oscular terminations. 
Flagellated chambers various in size, the largest about 0'0395 mm. in diameter when 
circular in section, and 0‘0355 by 0‘0434 mm. when oval. Apopyle 0'0158 mm. in 
diameter. 
Spicules. — I. Megascleres. 1. Oxea (PI. IX. fig. 2), straight or slightly curved, not 
very sharply pointed; 3 ‘57 by 0‘071 mm. 
2. Oxea (PI. IX. fig. 3), slender, cylindrical, sharply pointed, irregularly curved ; 
4'28 by 0'013 mm. 
3. Orthotrisene (PI. IX. fig, 4). With straight, conical, sharply pointed rhabdome 
and cladi; cladi slightly projecting forwards, sometimes retroflexed or bent laterally 
(PL IX. fig. 16) near the ends; rhabdome 0'714 by 0'071 mm.; cladi 0'357 mm. long. 
4. Calthrops (PL IX. fig. 5), of the usual form ; actines 0'4 by 0'048 mm. 
II. Microscleres. 5. Microxea (PL IX. figs. 6, 19-21), fusiform, sharply pointed, 
curved or somewhat sharply bent in the middle, roughened or minutely spined or smooth ; 
0T29 by 0’00395 mm. 
6. Metaster (PL IX. figs. 8-13), axis curved once, bearing spines on the convex 
side and at the ends, or straight and spined at the ends only ; rarely reduced to a 
plesiaster with three or four spines. Total length 0‘0316 mm., of a single spine 
0’0138 mm. 
7. Spiraster (PL IX. figs. 14, 15), spire of about two or three revolutions, extended 
on the outer side into a lamella or ala, bearing short, rod-like, abruptly truncated spines 
1 TroiKiMi, variegated, various. 
